1. Field of the Invention
The present invention relates to a method and an apparatus for nuclear magnetic resonance imaging for taking nuclear magnetic resonance images which are synchronous to the heart beat of a patient.
2. Description of the Background Art
In a conventional nuclear magnetic resonance imaging apparatus, the nuclear magnetic resonance images synchronous to the heart beat of a patient have been obtained by taking the electro-cardiogram of the patient, and generating synchronization signals such as QRS pulses Pr which are synchronized with the rise of the R wave, such that the nuclear magnetic resonance imaging is carried out by using the generated synchronization signals.
For example, in a case of taking the nuclear magnetic resonance images of the heart of the patient, the RF pulses are applied onto the patient in synchronization with the generated QRS pulses Pr, such that the nuclear magnetic resonance signals at different time sequence phases are collected with the QRS pulses Pr as the reference. Then, the nuclear magnetic resonance signals corresponding to each time sequence phase are selected from the collected nuclear magnetic resonance signals, such that the nuclear magnetic resonance image at each time sequence phase can be reconstructed and displayed.
However, as shown in FIG. 1, when the RF pulses are applied, the RF noises Wn are introduced into the electro-cardiographic wave Wh. As a result, not only the QRS pulses Pr are generated in response to the genuine electro-cardiographic wave Wh, but also the additional pulses Pr' are generated in response to these RF noises Wn. Moreover, this generation of the additional pulses Pr' occurs within the scanning interval Ts during which the nuclear magnetic resonance signals are collected, so that the synchronization of the nuclear magnetic resonance signals with the heart beat is disturbed and the quality of the reconstructed nuclear magnetic resonance images are deteriorated.